Remove the tough stems from the kale leaves and then tear the leaves into large pieces. Set aside.

Add the oil and preheat the pot to 300°F/148°C (medium-low).

Add the onion and cook for 2 minutes, stirring occasionally.

Add the chopped garlic and chili flakes to the onion and continue cooking for 30 seconds, stirring continuously.

The pot will be very full but the kale will wilt as it cooks.

Add the stock and the salt, and cover the pot with a tight fitting lid.

Reduce the heat to 220°F/104°C (low) and braise the kale for 25 minutes, stirring occasionally, always returning the lid back to the pot.

Remove the lid and continue cooking for 4 minutes to allow any extra liquid to evaporate, stirring occasionally.

Stir in the balsamic vinegar and parmesan cheese.

Remove from the heat and serve immediately. You can garnish with additional parmesan cheese if desired.